Peter Greenleaf is stepping down down as president of Gaithersburg-based biotechnology giant MedImmune, according to a company spokesman, to take the helm of parent company AstraZeneca’s Latin America business. He will be replaced by Bahija Jallal, who currently serves as MedImmune’s executive vice president of research and development. Jallal joined the company in 2006 as vice president of translational sciences. The leadership change comes as MedImmune was formally designated a biologics research and development site for AstraZeneca, meaning Jallal will report directly to AstraZeneca chief executive Pascal Soriot, said company spokesman Mike O’Brien. He added that MedImmune’s commercial organization will now report into AstraZeneca’s North American business and its manufacturing group will be folded into AstraZeneca’s global operations group. “There’s no new news on jobs today,” O’Brien said. “The driver for these changes is not cost but even faster decision-making in key areas of the business and a need to reduce complexity.” O’Brien said Greenleaf will continue to be based in Maryland, where he has become a figure­head of sorts for the life sciences industry.